1,1

All terms are primes.

There is no further term up to prime(1250). -Farideh Firoozbakht (mymontain(AT)yahoo.com), Apr 16 2007

a:=proc(n) if type((3^n+4^n)/7, integer)=true and isprime((3^n+4^n)/7)=true then n else fi end: seq(a(n), n=1..1500); -Emeric Deutsch (deutsch(AT)duke.poly.edu), Feb 17 2007

k=4; Do[ p=Prime[n]; f=(3^p+k^p)/(k+3); If[ PrimeQ[f], Print[p]], {n, 1, 100} ]

Cf. A007658 = numbers n such that (3^n + 1)/4 is prime. Cf. A057469 = numbers n such that (3^n + 2^n)/5 is prime. Cf. A122853 = numbers n such that (3^n + 5^n)/8 is prime. Cf. A128067, A128068, A128069, A128070, A128071, A128072, A128073, A128074, A128075. Cf. A059801 = numbers n such that 4^n - 3^n is prime. Cf. A121877 = numbers n such that (5^n - 3^n)/2 is a prime. Cf. A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128031, A128032.

Sequence in context: A068990 A062594 A128027 this_sequence A148523 A148524 A148525

Adjacent sequences: A128063 A128064 A128065 this_sequence A128067 A128068 A128069

hard,more,nonn

Alexander Adamchuk (alex(AT)kolmogorov.com), Feb 14 2007

3 more terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Feb 17 2007

2 more terms from Farideh Firoozbakht (mymontain(AT)yahoo.com), Apr 16 2007